posted on 2024-02-06, 22:04authored bySamuel Astier, Edwin C. Johnson, Oleta Norvilaite, Spyridon Varlas, Emma E. Brotherton, George Sanderson, Graham J. Leggett, Steven P. Armes
Sterically stabilized diblock copolymer nanoparticles
with a well-defined
spherical morphology and tunable diameter were prepared by RAFT aqueous
emulsion polymerization of benzyl methacrylate at 70 °C. The
steric stabilizer precursor used for these syntheses contained pendent cis-diol groups, which means that such nanoparticles can
react with a suitable aldehyde-functional surface via acetal bond
formation. This principle is examined herein by growing an aldehyde-functionalized
polymer brush from a planar silicon wafer and studying the extent
of nanoparticle adsorption onto this model substrate from aqueous
solution at 25 °C using a quartz crystal microbalance (QCM).
The adsorbed amount, Γ, depends on both the nanoparticle diameter
and the solution pH, with minimal adsorption observed at pH 7 or 10
and substantial adsorption achieved at pH 4. Variable-temperature
QCM studies provide strong evidence for chemical adsorption, while
scanning electron microscopy images recorded for the nanoparticle-coated
brush surface after drying indicate mean surface coverages of up to
62%. This fundamental study extends our understanding of the chemical
adsorption of nanoparticles on soft substrates.